The invention relates to an electrical.
Electrical switches such as these are used in electrical handheld tools, such as drills, angle grinders, circular saws, routers, hedge trimmers or the like. In particular, these may be electrical tools which are operated using direct current. Furthermore, switches such as these can switch with a delay, for example for soft starting on switching on and/or for short-circuit braking of the electrical tool.
An electrical switch which is suitable for short-circuit braking of the electrical tool is known from German patent document DE 42 32 402 A1. This switch has at least one contact system, which has a switching contact which can move between a switched-off position and a switched-on position for switching, and a stationary contact which interacts with the switching contact in the switched-on position. An operating member which can be moved manually acts on the switching contact, for switching. Furthermore, the switch has a delay means, which is operatively connected to the switching contact in one switch position in order to delay the switching movement.
The delay means, which is designed in the form of a delay drum, is arranged in the immediate vicinity, underneath the contact system, in the housing of the switch. The operating member is located above the contact system, on the opposite side of the housing. The switch thus has a considerable size, which may be an impediment in view of the fact that the spatial conditions in electrical tools are often confined. Furthermore, the means for the operative connection between the delay drum and the switching contact has a complex design. The means is expensive to manufacture, and its assembly is complex. The influences of faults during operation of the switch cannot in all cases be precluded and, in particular, an undesirable delay can occur in the switching movement of the switching contact when switching to the other switch position, as well.
An object of the invention is to provide a switch which has a delay means which interacts with the switching contact, has a physically small size, and/or has a switching delay to the one switch position that is not susceptible to defects.
A particularly compact switch is created in that the delay means and the operating member are arranged on the same side of the contact system. A switch which operates particularly reliably is, alternatively or additionally, created such that the operative connection between the delay means and the switching contact is reduced during the switching movement of the switching contact to the other switch position, in particular to the switched-off position, such that the switching contact moves to the other switching position essentially without any delay.
In general, the contact system is arranged in a housing. Up to four contact systems, which are located one behind the other, are preferably located in the housing. By way of example, two of these contact systems are used for the voltage supply with soft starting when the electric motor of the electrical tool is switched on, the third contact system is used for short-circuiting the electric motor for braking of the electrical tool when the voltage supply is switched off, and the fourth contact system is used as a bridge for the full voltage supply for the electric motor in the electrical tool after completion of the soft starting.
The operating member can be mounted on the upper face of the housing such that it can move. In one embodiment, a slide, which is guided into the housing and acts on a carriage, is articulated on the operating member. The switching contact is mounted elastically on the carriage with the aid of an elastic means, for example by means of a compression spring. Furthermore, a first spring, which is used to produce a pressure point or pressure points for the switching movement and interacts with the housing, can be arranged on the carriage. In addition, a second spring, which interacts with the slide and assists a snap-action switching movement, can also be arranged. Furthermore, a third spring, which is used for resetting, may also be located on the slide.
In one development, a guide channel for the slide is located on the upper face of the housing. The delay means can then be arranged on the upper face in the housing, and in an extension of the guide channel. The delay means may be in the form of a delay drum. A housing attachment which, in particular has an approximately half-cylindrical shape, is preferably arranged on the upper face of the housing, for holding and providing a bearing for the delay drum.
In one refinement, the delay means has a cylindrical drum, which is filled with a viscous liquid, and a shaft, which is arranged in the cylindrical drum, so that the cylindrical drum can move in a damped manner relative to the shaft. One shaft end may project on one side out of the cylindrical drum. Furthermore, a tooth system can be fitted on the cylindrical drum, in particular in the form of a pinion on that side of the cylindrical drum which is opposite the shaft end. A transmission element can then be moved in a damped manner by the cylindrical drum in order to act on the switching contact by means of a mating tooth system.
In a further refinement, a sliding element, which acts against the elastic means for the bearing of the switching contact, is mounted in the carriage such that it can move. The transmission element can then be coupled to the sliding element such that the restraining force which is exerted by the delay means acts against the force which is exerted by the elastic means during the switching movement of the switching contact, in order to delay the switching movement.
In one development, the transmission element is in the form of an approximately circular annular element. A shaft stub can be arranged on the periphery of the annular element facing away from the sliding element and engages in a bearing point in the housing attachment in order to allow the annular element to rotate through an angle which is defined in particular by stops in the housing attachment. An attachment for coupling to the sliding element can be fitted, approximately opposite the shaft stub, on the periphery of the annular element.
As a further embodiment, it is possible to fit the mating tooth system in the manner of an internal tooth system on the annular element. By way of example, the internal tooth system may be approximately in the form of a circular section. The sliding element may have an approximately U-shaped holder, in which the attachment on the annular element engages. Furthermore, the switching contact and the sliding element may be arranged on that side of the carriage which faces away from the delay means. The U-shaped holder may project through an aperture in the carriage, on that side of the carriage which faces the delay means.
In a further refinement, the transmission element has two annular elements, which are separated from one another by approximately the height of the cylindrical drum for the delay means. A shaft stub is preferably in each case located on each annular element, in order to mount the transmission element in a respective associated bearing point in the housing attachment. However, an internal tooth system may be fitted only on that annular element which faces away from the shaft end of the delay means. The attachments may be in the form of a rod element which connects the two annular elements to one another. Finally, the rod element may have a reduction in its cross section approximately in the center, by means of which the rod element engages in the U-shaped holder on the sliding element.
Advantages which are achieved by the invention are, in particular, that, despite having a high performance, the electrical switch occupies only a small installation area in the electrical tool. The switch is thus particularly suitable for installation in slimline, ergonomically shaped, handles of electrical tools. Since the effectiveness of the delay means can be restricted to one switching direction, any arc which may occur when switching off the electrical tool is extinguished immediately, thus effectively preventing destruction of the contact system, and lengthening the life of the switch. The switch is thus suitable for high currents, in particular for direct-current applications as well. It is likewise possible to use the switch as a braking switch. The configuration of the transmission element, which provides the coupling between the delay means and the switching contact, means that, despite its compactness, the transmission element can travel through large angular intervals with little space being required. This once again advantageously ensures that even lengthy delay times can be set, as required. Finally, the switch also has a comparatively small number of individual parts, so that it can be produced at very low cost.